1. Field of the Invention
The invention relates to an electric switch device, and more particularly, to an electric switch device which can prevent damages to it and devices connected to it.
2. Description of the Prior Art
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a cross-sectional view of a prior art electric switch device 10 in an "off" status. FIG.2 is a cross-sectional view of the electric switch device 10 in FIG.1 in an "on" status. The electric switch device 10 comprises a housing 12, two electric terminals 14 and 16, a button 18, a conductive reed 20, a connecting rod 26 connected between the button 18 and the reed 20, and an elastic piece 24 installed between the housing 12 and a front end of the reed 20 for elastically fixing the front end of the reed 20 in an "up" position (as shown in FIG. 1) or in a "down" (as shown in FIG. 2) position. The button 18 can be depressed to toggle between the "on" status and the "off" status. When a first end 19 of the button 18 is depressed, the connecting rod 26 will push the reed 20 downward to connect the two electric terminals 14, 16, and the elastic piece 24 will elastically move and fix the front end of the reed 20 to the "down" position. Then, the reed 20 connects the two electric terminals 14, 16 and allows electric current to pass between the two electric terminals 14, 16 (as shown in FIG. 2). When a second end 21 of the button 18 is depressed, the connecting rod 26 will move the reed 20 upward, and the elastic piece 24 will elastically move and fix the front end of the reed 20 in the "up" position. Then, the electric terminal 14 will disconnect from the electric terminal 16 thus disabling electric current from passing between the two electric terminals 14, 16.
The reed 20 is formed by combining two metal pieces of different heat expansion coefficients whereby when the current passing through the reed 20 exceeds the predetermined current level, the front end of the reed 20 will spring upward because of the heat generated by the current. When the reed 20 springs upward to push the connecting rod 26 and the button 18 upward, the button 18 will be set "off". At this time, if the user depresses the button 18 to set the electric switch device 10 "on", the electric switch device 10 and the device connected to the electric switch device 10 will be damaged. Furthermore, if the button is damaged or becomes depressed such that it cannot be switched and the current passing through the reed 20 exceeds the predetermined current level, the reed 20 cannot spring upward. Therefore, the electric terminal 14 can not disconnect from the electric terminal 16 and the electric switch device 10 remains "on". This may damage the electric switch device 10 and devices connected to the electric switch device 10.